Silicon has a density of 2.33 g/cm^3 and an atomic mass of 28.09 g/mol. A 0.2-mm thick wafer is treated so that a uniform concentration gradient of antimony is produced. One surface contains 10 Sb atom per 10^8 Si atoms and the other surface contains 500 Sb atoms per 10^8 Si atoms. Calculate the concentration gradient in Sb atoms/cm^3.cm.

An unknown substance is a white solid at room temperature and has a melting point of 78 °c. which of the following substances is most likely to be the identity of the unknown sample? a. naphthalene, a molecular solid with the formula c10h8 b. silica, a network solid held together by covalent bonds with the formula sio2 c. calcium chloride, an ionic compound with the formula cacl2 d. water, an molecular compound with the formula h2o